If you're going to strip till, having your own or paying for a higher level GPS is part of the program for most people. 

If you are small time and not spread out, get two used RTK ready receivers and run your own base. Paying no one, even charge other neighbors to use it if you want. 

Or get a used SF3 ready 6000 globe and run SF3. Don't run SF2, it's the same price as SF3 and not as accurate. (which is why it's going away soon)